Commercially available audio cable, used to interconnect audio components such as compact disc players, amplifiers and speakers, transmits different frequency signals within the audio frequency range at different velocities of propagation. The audio frequency range is generally considered to include frequencies from about 15 Hz to about 20 kHz while the radio frequency range is generally considered to extend upwardly from about 150 kHz. Standard audio cable transmits signals near the lower end of the audio frequency range, such as signals resulting from base instruments, at velocities of propagation below about 10% of the speed of light (c). On the other hand, standard audio cable transmits high frequency audio signals, such as one resulting from a violin, at velocities of propagation above about 30% of c. These great differences in the velocities of propagation result in substantial distortion of the output signals.
Various cables, including a metallic core and a surrounding sleeve of magnetically permeable material (such as ferrite), have been proposed for transmission of radio frequency signals to reduce radio frequency attenuation. For further information concerning the structure and operation of such cables, reference may be made to U.S. Pat. Nos. 2,787,656; 3,238,477; 4,079,192; 4,515,826; and 4,587,133.
U.S. Pat. No. 4,695,127 discloses a coaxial cable including a metallic core with a coaxial metallic shield formed by a metallic braid over a metallic foil.